• Preheat your oven to 350°F (177°C). Grease and flour a 9-inch round cake pan.

Prepare the Cake:

• In a mixing bowl, beat the sugar and eggs together until light and fluffy. Add the flour, milk, butter, and vanilla, and mix until smooth. Pour the batter into the prepared cake pan and bake for about 20 minutes, or until a toothpick inserted into the center comes out clean. Allow the cake to cool on a wire rack.

Make the Custard Filling:

• In a saucepan, whisk together milk, sugar, and cornstarch over medium heat until it starts to thicken. Temper the egg yolks by adding a small amount of the hot mixture to the yolks, then return it all to the saucepan. Stir constantly until the custard is thick and bubbly. Remove from heat, stir in butter and vanilla, then let cool.

Prepare the Chocolate Glaze:

• Heat the heavy cream in a small saucepan until it just begins to simmer. Pour it over the chopped chocolate in a bowl. Let it sit for a minute, then stir until smooth and glossy.

To Assemble:

• Slice the cooled cake into two layers with a serrated knife. Spread the custard filling on the bottom half, then place the other half on top. Pour the chocolate glaze over the top of the cake, allowing it to drip down the sides.